(i) An aqueous solution of a white coloured compound `(A)` on reaction with `HCl` gives a white precipitate of compound `(B)`.
(ii) `(B)` becomes soluble in chlorine water with the formation of `(C)`
(iii) `(C)` reacts with `KI` to give a precipitate which becomes solube in excess of it forming a compount `(D)`. the compound `(D)` is used for detecting ammonium salts.
(iv) `(B)` and `(C)` both, on treatement with `SnCl_(2)` give a grey precipitate of `(E)`.
(v) When conc. `H_(2)SO_(4)` is added slowly into a mixture of cold solutions of `(A)` and `FeSO_(4)` is added slowly into a mixture of cold solutions of `(A)` and `FeSO_(4)`, a brown ring of compound `(F)` is formed.
The oxidation number of `FE` in compound `(F)` is:

Options

A. `+1`
B. `+2`
C. `+3`
D. zero

Explanation

No in iron complex has oxidation no. `+1`
`:. Fe` in `feSO_(4).NO` is in +1